Blood Flow and Oxygen Consumption in Muscles after Section of Ventral Roots

Abstract

Muscles deprived of somatic motor innervation (sensory and sympathetic motor innervation intact) served as a model for studying the role of vasoconstrictor fibers and skeletal muscle tone in the regulation of skeletal muscle blood flow. Blood flow, vascular resistance and O² consumption of the gastrocnemius muscle of the cat were measured 5 to 7, 10 to 16, and 27 to 44 days after unilateral section of ventral roots L⁵ to S⁵ in cats and compared to similar measurements in the normal gastrocnemius muscle and in that with its sciatic nerve cut. After section of the peripheral nerve, total blood flow increased and then returned to normal; after section of the ventral roots, total blood flow did not change significantly. In both cases, blood flow per 100 g of muscle increased as atrophy developed. After section of the ventral roots, O² consumption and CO² production per 100 g of muscle increased earlier than blood flow. Peripheral resistance was calculated before and immediately after acute section of both tibial nerves to evaluate the participation of muscle tone in the regulation of peripheral resistance. At rest, muscle tone appears to be responsible for about 25% of the peripheral resistance.